1. Field of the Invention
This invention relates to a magneto-optical signal reproducing apparatus for reproducing data from a magneto-optical signal obtained from a magneto-optical recording medium.
2. Related Art Statement
In the prior art, data are reproduced from a magneto-optical recording medium, for example, a magneto-optical disk, by focusing a laser beam on the magneto-optical recording medium. A reflected light or a transmitted light is thereafter detected by means of a photo detector, included in an optical pickup device. A difference between detected polarized light components, which are different from each other, provides a magneto-optical signal. This magneto-optical signal is level-discriminated on the basis of a predetermined reference level, or a threshold level, to provide a binary signal which is demodulated/decoded so as to reproduce the data therefrom.
If the level of a signal detected by the photo detector of the optical pickup device changes due to defects related to the recording medium which, for example, may be caused by disturbances at the time of recording or reproducing, or the like, there is a possibility that the level discrimination utilized in forming the binary signal, or the binarization thereof, is not properly conducted.
For this reason, in the prior art, the magneto-optical signal provided from the optical pickup device is delivered to an AGC (automatic gain control) circuit for conducting an automatic gain control thereon. However, in the case of a magneto-optical storage disk, a signal stored thereon typically has a broad frequency band which, for example, may be between 10 Hz and 20 MHz. As a result, a high speed AGC is required which, in turn, results in a relatively complicated circuit configuration and/or increased cost.